Power transmission apparatus for vehicle

The present application claims priority to Korean Patent Application No. 10-2015-0170230, filed Dec. 1, 2015, the entire contents of which is incorporated herein for all purposes by this reference.

The present invention relates to a power transmission apparatus for a vehicle. More particularly, the present invention relates to a power transmission apparatus for a vehicle that realizes eight forward speed stages and one reverse speed stage using two synchronizers and two planetary gear sets.

Environmentally-friendly technique of vehicles is very important technique on which survival of future motor industry is dependent. Vehicle makers are focusing on development of environmentally-friendly vehicles so as to meet environment and fuel consumption regulations.

Some examples of future vehicle technique are an electric vehicle (EV) and a hybrid electric vehicle (HEV) that use electrical energy, and double clutch transmission (DCT) that improves efficiency and convenience.

The DCT includes two clutch devices and a gear train of a manual transmission. The DCT selectively transmits torque input from an engine to two input shafts through two clutches, changes the torque selectively transmitted to the two input shafts through the gear train, and outputs the changed torque.

The DCT is used to realize a compact transmission achieving a forward speed stage higher than a fifth forward speed stage. The DCT is used as an automated manual transmission that does not require a driver's manual manipulation by controlling two clutches and synchronizing devices by a controller.

Compared with an automatic transmission with planetary gear sets, the DCT has excellent power delivery efficiency, simplifies change and addition of components for achieving multiple gear stages, and improves fuel economy.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Various aspects of the present invention are directed to providing a power transmission apparatus for a vehicle having advantages of achieving eight forward speed stages and a reverse speed stage, realizing multiple speed stages, and improving fuel economy by adding two planetary gear sets to a DCT including two synchronizers.

Various aspects of the present invention are additionally directed to providing a power transmission apparatus for a vehicle having further advantages of simplifying an interior layout and minimizing weight of the power transmission apparatus by reducing the number of components, and of improving fuel economy by achieving eight forward speed stages and one reverse speed stage with two synchronizers and two planetary gear sets.

According to various aspects of the present invention, a power transmission apparatus for a vehicle may include a first input shaft directly connected to an engine, a second input shaft surrounding the first input shaft without rotational interference with the first input shaft and selectively receiving torque of the engine through a first clutch, a third input shaft surrounding the second input shaft without rotational interference with the second input shaft and selectively receiving the torque of the engine through a second clutch, an intermediate shaft disposed parallel to the first, second, and third input shafts, a transfer gear fixedly disposed on the intermediate shaft and outputting torque of the intermediate shaft, a first shifting member receiving the torque of the engine from the third input shaft, changing the torque of the engine into first and second preliminarily shifted torques, and outputting the first and second preliminarily shifted torques, a second shifting member receiving the torque of the engine from the second input shaft, changing the torque of the engine into third and fourth preliminarily shifted torques, and outputting the third and fourth preliminarily shifted torques, and a third shifting member changing the torque of the engine directly transmitted from the first input shaft and the first preliminarily shifted torque to the fourth preliminarily shifted torque selectively transmitted from the first shifting member or the second shifting member into eight forward speed stages and one reverse speed stage, and outputting the eight forward speed stages and the one reverse speed stage.

The first shifting member may include a 1/7 drive gear and a 3/5 drive gear fixedly disposed on the third input shaft, a 1/7 driven gear rotatably disposed on the intermediate shaft and engaged with the 1/7 drive gear, a 3/5 driven gear rotatably disposed on the intermediate shaft and engaged with the 3/5 drive gear, and a first synchronizer operably connecting the 1/7 driven gear or the 3/5 driven gear to the intermediate shaft selectively.

The first shifting member may include a 1/7 drive gear and a 3/5 drive gear rotatably disposed on the third input shaft, a first synchronizer operably connecting the 1/7 drive gear or the 3/5 drive gear to the third input shaft selectively, a 1/7 driven gear fixedly disposed on the intermediate shaft and engaged with the 1/7 drive gear, and a 3/5 driven gear fixedly disposed on the intermediate shaft and engaged with the 3/5 drive gear.

The second shifting member may include an 8/R drive gear rotatably disposed on the second input shaft, a 2/6 drive gear rotatably disposed on the second input shaft and engaged with the transfer gear on the intermediate shaft, a second synchronizer operably connecting the 8/R drive gear or the 2/6 drive gear to the second input shaft selectively, and an 8/R driven gear fixedly disposed on the intermediate shaft and operably connected to the 8/R drive gear through an idle gear.

The third shifting member may include a first planetary gear set including a first sun gear, a first planet carrier, and a first ring gear as rotation elements thereof, a second planetary gear set including a second sun gear, a second planet carrier, and a second ring gear as rotation elements thereof, four rotation shafts directly connected to at least one of the rotation elements of the first planetary gear set and the second planetary gear set, and frictional elements, at least one of the frictional elements selectively connecting at least of the four rotation shafts to the first input shaft or selectively connecting one rotation element of the first planetary gear set to one rotation element of the second planetary gear set, and remaining frictional elements selectively connecting another rotation shaft among the four rotation shafts to a transmission housing.

Each of the first planetary gear set and the second planetary gear set may be a single pinion planetary gear set, and the four rotation shafts may include a first rotation shaft directly connecting the first sun gear with the second sun gear and receiving torque from the first shifting member and the second shifting member, a second rotation shaft directly connected to the second planet carrier and directly connected to the first input shaft, a third rotation shaft directly connected to the first planet carrier, directly connected to an output shaft, and selectively connectable to the second ring gear, a fourth rotation shaft directly connected to the first ring gear and selectively connectable to the transmission housing.

The frictional elements may include a third clutch disposed between the first planet carrier and the second ring gear, and a brake disposed between the fourth rotation shaft and the transmission housing.

Each of the first planetary gear set and the second planetary gear set may be a single pinion planetary gear set, the four rotation shafts may include a first rotation shaft directly connecting the first sun gear to the second sun gear and receiving torque from the first shifting member and the second shifting member, a second rotation shaft directly connected to the second planet carrier and selectively connectable to the first input shaft, a third rotation shaft directly connecting the first planet carrier to the second ring gear and directly connected to an output shaft, and a fourth rotation shaft directly connected to the first ring gear and selectively connectable to the transmission housing.

The frictional elements may include a third clutch disposed between the first input shaft and the second rotation shaft, and a brake disposed between the fourth rotation shaft and the transmission housing.

Each of the first planetary gear set and the second planetary gear set may be a single pinion planetary gear set, and the four rotation shafts may include a first rotation shaft directly connected to the first sun gear, selectively connectable to the second sun gear, and receiving torque from the first shifting member and the second shifting member, a second rotation shaft directly connected to the second planet carrier and directly connected to the first input shaft, a third rotation shaft directly connecting the first planet carrier to the second ring gear and directly connected to an output shaft, and a fourth rotation shaft directly connected to the first ring gear and selectively connectable to the transmission housing.

The frictional elements may include a third clutch disposed between the first sun gear and the second sun gear, and a brake disposed between the fourth rotation shaft and the transmission housing.

Each of the first planetary gear set and the second planetary gear set may be a single pinion planetary gear set, and the four rotation shafts may include a first rotation shaft directly connected to the first sun gear and receiving torque from the first shifting member and the second shifting member, a second rotation shaft directly connecting the first planet carrier to the second ring gear and selectively connectable to the first input shaft, a third rotation shaft directly connecting the first ring gear to the second planet carrier and directly connected to an output shaft, and a fourth rotation shaft directly connected to the second sun gear and selectively connectable to the transmission housing.

The third shifting member may be a Ravingneaux compound planetary gear set in which a single pinion planetary gear set and a double pinion planetary gear set are combined with each other to use a planet carrier and a ring gear in common, and the third shifting member may include four rotation shafts, and frictional elements, at least one of the frictional elements selectively connecting at least one rotation shaft among the four rotation shafts to the first input shaft, and another of the frictional elements selectively connecting another rotation shaft among the four rotation shafts to a transmission housing.

The four rotation shafts may include a first rotation shaft directly connected to a sun gear of the single pinion planetary gear set and receiving torque from the first shifting member and the second shifting member, a second rotation shaft directly connected to a common planet carrier and selectively connectable to the first input shaft, a third rotation shaft directly connected to a common ring gear and directly connected to an output shaft, and a fourth rotation shaft directly connected to a sun gear of the double pinion planetary gear set and selectively connectable to the transmission housing.

Various embodiments of the present invention may achieve one reverse speed stage and eight forward speed stages by adding two planetary gear sets to a DCT provided with two synchronizers. Therefore, multiple speed stages are achieved and fuel economy is improved.

In addition, an interior layout may be simplified, length and weight of the DCT may be minimized by reducing the number of components.

In addition, since even-numbered speed stages and odd-numbered speed stages are achieved by turns by alternately operating two clutches, smooth shift may be achieved.

It is understood that the term “vehicle” or “vehicular” or other similar terms as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuel derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example, both gasoline-powered and electric-powered vehicles.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

FIG. 1 is a schematic diagram of a power transmission apparatus for a vehicle according to various embodiments of the present invention.

FIG. 2 is an operational chart of a power transmission apparatus for a vehicle according to various embodiments of the present invention.

FIG. 3 is a lever diagram of a power transmission apparatus for a vehicle according to various embodiments of the present invention.

FIG. 4 is a schematic diagram of a power transmission apparatus for a vehicle according to various embodiments of the present invention.

FIG. 5 is a schematic diagram of a third shifting member of a power transmission apparatus for a vehicle according to various embodiments of the present invention.

FIG. 6 is a schematic diagram of a third shifting member of a power transmission apparatus for a vehicle according to various embodiments of the present invention.

FIG. 7 is a schematic diagram of a third shifting member of a power transmission apparatus for a vehicle according to various embodiments of the present invention.

FIG. 8 is a schematic diagram of a third shifting member of a power transmission apparatus for a vehicle according to various embodiments of the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

FIG. 1 is a schematic diagram of a power transmission apparatus for a vehicle according to a first exemplary embodiment of the present invention.

Referring to FIG. 1 , torque of an engine ENG that is a power source is changed into four preliminarily shifted torques through a first shifting member T 1 and an second shifting member T 2 and the four preliminarily shifted torques are transmitted to a third shifting member T 3 in a power transmission apparatus according to the first exemplary embodiment of the present invention. The four preliminarily shifted torques, together with the torque of the engine ENG directly input to the third shifting member T 3 is changed into eight forward speed stages and a reverse speed stage, and the eight forward speed stages and the reverse speed stage are output.

The engine ENG that is the power source may be a gasoline engine or a diesel engine using a fossil fuel.

The torque generated in the engine ENG is transmitted to the third shifting member T 3 , the second shifting member T 2 and the first shifting member T 1 through first, second, and third input shafts IS 1 , IS 2 , and IS 3 .

The first input shaft IS 1 is directly connected to an output side of the engine ENG and directly transmits torque of the engine ENG to the third shifting member T 3 .

The second input shaft IS 2 is a hollow shaft, encloses the first input shaft IS 1 without rotational interference therewith, is selectively connectable to the output side of the engine ENG through a first clutch CL 1 , and selectively transmits the torque of the engine ENG to the second shifting member T 2 .

The third input shaft IS 3 is a hollow shaft, encloses the second input shaft IS 2 without rotational interference therewith, is selectively connectable to the output side of the engine ENG through a second clutch CL 2 , and selectively transmits the torque of the engine ENG to the first shifting member T 1 .

The first shifting member T 1 includes a 1/7 drive gear D 1 / 7 and a 3/5 drive gear D 3 / 5 fixedly disposed on the third input shaft IS 3 , a 1/7 driven gear P 1 / 7 disposed on an intermediate shaft CS disposed in parallel with the third input shaft IS 3 and engaged with the 1/7 drive gear D 1 / 7 , a 3/5 driven gear P 3 / 5 disposed on the intermediate shaft CS and engaged with the 3/5 drive gear D 3 / 5 , and a first synchronizer SL 1 disposed on the intermediate shaft CS.

The 1/7 driven gear P 1 / 7 and the 3/5 driven gear P 3 / 5 are rotatably disposed on the intermediate shaft CS.

The first synchronizer SL 1 operably connects the 1/7 driven gear P 1 / 7 or the 3/5 driven gear P 3 / 5 to the intermediate shaft CS selectively. Therefore, the intermediate shaft CS transmits torque selectively transmitted through the 1/7 driven gear P 1 / 7 or the 3/5 driven gear P 3 / 5 to the second shifting member T 2 through a transfer gear TFG fixedly disposed on the intermediate shaft CS. The torque transmitted to the second shifting member T 2 is then transmitted to the third shifting member T 3 .

Therefore, the first shifting member T 1 generates a first preliminarily shifted torque for achieving a first forward speed stage and a seventh forward speed stage, and a second preliminarily shifted torque for achieving a third forward speed stage and a fifth forward speed stage.

The second shifting member T 2 includes an 8/R drive gear D 8 /R and a 2/6 drive gear D 2 / 6 disposed on the second input shaft IS 2 extended to the rear of the third input shaft IS 3 , a second synchronizer SL 2 disposed on the second input shaft IS 2 extended to the rear of the third input shaft IS 3 , an 8/R driven gear P 8 /R fixedly disposed on the intermediate shaft CS and operably connected to the 8/R drive gear D 8 /R, and an idle gear IDG engaged with the 8/R drive gear D 8 /R and the 8/R driven gear P 8 /R.

The 8/R drive gear D 8 /R and the 2/6 drive gear D 2 / 6 are rotatably disposed on the second input shaft IS 2 , and the idle gear IDG is fixedly disposed on an idle shaft IDS disposed in parallel with the second input shaft IS 2 . The idle gear IDG causes the 8/R driven gear P 8 /R and the 8/R drive gear D 8 /R to rotate in the same direction.

The second synchronizer SL 2 operably connects the 8/R drive gear D 8 /R or the 2/6 drive gear D 2 / 6 to the second input shaft IS 2 selectively.

In addition, the transfer gear TFG fixedly disposed on a rear portion of the intermediate shaft CS and engaged with the 2/6 drive gear D 2 / 6 is not concerned in achieving even-numbered speed stages, and transmits the torque transmitted from the first shifting member T 1 to the third shifting member T 3 through the 2/6 drive gear D 2 / 6 .

In addition, the 2/6 drive gear D 2 / 6 transmits torque transmitted from the second input shaft IS 2 to the third shifting member T 3 without rotation speed change, or changes rotation speed of the second input shaft IS 2 according to gear ratios of the transfer gear TFG and the 2/6 drive gear D 2 / 6 engaged with each other and transmits the changed rotation speed to the third shifting member T 3 .

Therefore, the second shifting member T 2 generates a third preliminarily shifted torque for achieving a second forward speed stage and a sixth forward speed stage, and a fourth preliminarily shifted torque for achieving an eighth forward speed stage and a reverse speed stage. Gear ratio at the third preliminarily shifted torque is 1.0. Therefore, the same rotation speed as that of the engine ENG is output at the third preliminarily shifted torque.

The third shifting member T 3 includes first and second planetary gear sets PG 1 and PG 2 , one clutch CL 3 and one brake BK.

The first planetary gear set PG 1 is a single pinion planetary gear set and includes a first sun gear S 1 , a first planet carrier PC 1 rotatably supporting a first pinion P 1 that is externally meshed with the first sun gear S 1 , and a first ring gear R 1 that is internally meshed with the first pinion P 1 as rotation elements thereof.

The second planetary gear set PG 2 is a single pinion planetary gear set and includes a second sun gear S 2 , a second planet carrier PC 2 rotatably supporting a second pinion P 2 that is externally meshed with the second sun gear S 2 , and a second ring gear R 2 that is internally meshed with the second pinion P 2 as rotation elements thereof.

Since the first sun gear S 1 is directly connected to the second sun gear S 1 and the first planet carrier PC 1 is selectively connectable to the second ring gear R 2 , the first and second planetary gear sets PG 1 and PG 2 include four rotation shafts TM 1 to TM 4 .

The four rotation shafts TM 1 to TM 4 will be described in detail.

The first rotation shaft TM 1 directly connects the first sun gear S 1 to the second sun gear S 2 and is directly connected to the 2/6 drive gear D 2 / 6 .

The second rotation shaft TM 2 is directly connected to the second planet carrier PC 2 and is directly connected to the first input shaft IS 1 .

The third rotation shaft TM 3 is directly connected to the first planet carrier PC 1 , is directly connected to the output shaft OS so as to be continuously operated as an output element, and is selectively connectable to the second ring gear R 2 .

The fourth rotation shaft TM 4 is directly connected to the first ring gear R 1 and is selectively connectable to a transmission housing H so as to be operated as a selective fixed element.

The first planet carrier PC 1 directly connected to the third rotation shaft TM 3 is selectively connectable to the second ring gear R 2 through the third clutch CL 3 , and the first ring gear R 1 directly connected to the fourth rotation shaft TM 4 is selectively connectable to the transmission housing H through the brake BK.

The third clutch CL 3 is released when only the first planetary gear set PG 1 is concerned with shifting and is operated when both of the first and second planetary gear sets PG 1 and PG 2 are operated as a compound planetary gear set.

The output shaft OS directly connected to the third rotation shaft TM 3 transmits the torque output from the third shifting member T 3 to a final speed reduction unit of a differential apparatus.

Since the first and second synchronizers SL 1 and SL 2 are well known to a person of an ordinary skill in the art, detailed description thereof will be omitted. In addition, first and second sleeves SLE 1 and SLE 2 applied respectively to the first and second synchronizers SL 1 and SL 2 , as well known to a person of an ordinary skill in the art, are operated by additional actuators and the actuators are controlled by a transmission control unit.

FIG. 2 is an operational chart of a power transmission apparatus for a vehicle according to the first exemplary embodiment of the present invention, and FIG. 3 is a lever diagram of a power transmission apparatus for a vehicle according to the first exemplary embodiment of the present invention. Referring to FIG. 2 and FIG. 3 , shifting processes of the power transmission apparatus will be described in detail.

The third clutch CL 3 is not operated and only the first planetary gear set PG 1 is concerned with the shifting at the first to the fourth forward speed stages and the reverse speed stage. On the contrary, the third clutch CL 3 is operated and both of the first and second planetary gear sets PG 1 and PG 2 are concerned with the shifting as the compound planetary gear set at the forward fourth to the eighth forward speed stages.

[Reverse Speed Stage]

As shown in FIG. 2 , the 8/R drive gear D 8 /R is operably connected to the second input shaft IS 2 through the sleeve SLE 2 of the second synchronizer SL 2 and the first clutch CL 1 and the brake BK are operated at the reverse speed stage REV.

Therefore, the torque of the engine ENG is shifted into the fourth preliminarily shifted torque through the first clutch CL 1 , the second input shaft IS 2 , the 8/R drive gear D 8 /R, the idle gear IDG, the 8/R driven gear P 8 /R, the intermediate shaft CS, the transfer gear TFG, and the 2/6 drive gear D 2 / 6 , and the fourth preliminarily shifted torque is input to the first rotation shaft TM 1 of the third shifting member T 3 as inverse rotation speed.

As shown in FIG. 3 , since the fourth rotation shaft TM 4 is operated as a fixed element by operation of the brake BK in a state that the fourth preliminarily shifted torque is input to the first rotation shaft TM 1 , a reverse shift line SR is formed in the third shifting member T 3 . Therefore, a gear ratio of REV is output through the third rotation shaft TM 3 that is an output member.

[First Forward Speed Stage]

As shown in FIG. 2 , the 1/7 driven gear P 1 / 7 is operably connected to the intermediate shaft CS through the sleeve SLE 1 of the first synchronizer SL 1 , and the second clutch CL 2 and the brake BK are operated at the first forward speed stage D 1 .

Therefore, the torque of the engine ENG is shifted into the first preliminarily shifted torque through the second clutch CL 2 , the third input shaft IS 3 , the 1/7 drive gear D 1 / 7 , the 1/7 driven gear P 1 / 7 , the intermediate shaft CS, the transfer gear TFG, and the 2/6 drive gear D 2 / 6 , and the first preliminarily shifted torque is input to the first rotation shaft TM 1 of the third shifting member T 3 .

As shown in FIG. 3 , since the fourth rotation shaft TM 4 is operated as the fixed element by operation of the brake BK in a state that the first preliminarily shifted torque is input to the first rotation shaft TM 1 , a first shift line SP 1 is formed in the third shifting member T 3 . Therefore, a gear ratio of D 1 is output through the third rotation shaft TM 3 that is the output member.

[Second Forward Speed Stage]

As shown in FIG. 2 , the 2/6 drive gear D 2 / 6 is operably connected to the second input shaft IS 2 through the sleeve SLE 2 of the second synchronizer SL 2 , and the first clutch CL 1 and the brake BK are operated at the second forward speed stage D 2 .

Therefore, the torque of the engine ENG is shifted into the third preliminarily shifted torque through the first clutch CL 1 , the second input shaft IS 2 , and the 2/6 drive gear D 2 / 6 , and the third preliminarily shifted torque is input to the first rotation shaft TM 1 of the third shifting member T 3 .

As shown in FIG. 3 , since the fourth rotation shaft TM 4 is operated as the fixed element by operation of the brake BK in a state that the third preliminarily shifted torque is input to the first rotation shaft TM 1 , a second shift line SP 2 is formed in the third shifting member T 3 . Therefore, a gear ratio of D 2 is output through the third rotation shaft TM 3 that is the output member.

[Third Forward Speed Stage]

As shown in FIG. 2 , the 3/5 driven gear P 3 / 5 is operably connected to the intermediate shaft CS through the sleeve SLE 1 of the first synchronizer SL 1 , and the second clutch CL 2 and the brake BK are operated at the third forward speed stage D 3 .

Therefore, the torque of the engine ENG is shifted into the second preliminarily shifted torque through the second clutch CL 2 , the third input shaft IS 3 , the 3/5 drive gear D 3 / 5 , the 3/5 driven gear P 3 / 5 , the intermediate shaft CS, the transfer gear TFG, and the 2/6 drive gear D 2 /, and the second preliminarily shifted torque is input to the first rotation shaft TM 1 of the third shifting member T 3 .

As shown in FIG. 3 , since the fourth rotation shaft TM 4 is operated as the fixed element by operation of the brake BK in a state that the second preliminarily shifted torque is input to the first rotation shaft TM 1 , a third shift line SP 3 is formed in the third shifting member T 3 . Therefore, a gear ratio of D 3 is output through the third rotation shaft TM 3 that is the output member.

[Forward Fourth Speed Shift-Stage]

As shown in FIG. 2 , both of the first and second synchronizers SL 1 and SL 2 maintain neutral states, and the third clutch CL 3 and the brake BK are operated at the forward fourth speed shift-stage D 4 . In this case, the first and second planetary gear sets PG 1 and PG 2 are operated as the compound planetary gear set.

Since the torque of the engine ENG is input to the second rotation shaft TM 2 through the first input shaft IS 1 and the fourth rotation shaft TM 4 is operated as the fixed element by operation of the brake BK, a fourth shift line SP 4 is formed in the third shifting member T 3 . Therefore, a gear ratio of D 4 is output through the third rotation shaft TM 3 that is the output member.

[Fifth Forward Speed Stage]

As shown in FIG. 2 , the 3/5 driven gear P 3 / 5 is operably connected to the intermediate shaft CS through the sleeve SLE 1 of the first synchronizer SL 1 , and the second clutch CL 2 and the third clutch CL 3 are operated at the fifth forward speed stage D 5 .

Therefore, the torque of the engine ENG is shifted into the second preliminarily shifted torque through the second clutch CL 2 , the third input shaft IS 3 , the 3/5 drive gear D 3 / 5 , the 3/5 driven gear P 3 / 5 , the intermediate shaft CS, the transfer gear TFG, and the 2/6 drive gear D 2 / 6 , and the second preliminarily shifted torque is input to the first rotation shaft TM 1 of the third shifting member T 3 .

In addition, the torque of the engine ENG is input to the second rotation shaft TM 2 of the third shifting member T 3 through the first input shaft IS 1 .

As shown in FIG. 3 , since the second preliminarily shifted torque is input to the first rotation shaft TM 1 and the torque of the engine ENG is input to the second rotation shaft TM 2 , a fifth shift line SP 5 is formed in the third shifting member T 3 . Therefore, a gear ratio of D 5 is output through the third rotation shaft TM 3 that is the output member.

[Sixth Forward Speed Stage]

As shown in FIG. 2 , the 2/6 drive gear D 2 / 6 is operably connected to the second input shaft IS 2 through the sleeve SLE 2 of the second synchronizer SL 2 , and the first clutch CL 1 and the third clutch CL 3 are operated at the sixth forward speed stage D 6 .

Therefore, the torque of the engine ENG is shifted into the third preliminarily shifted torque through the first clutch CL 1 , the second input shaft IS 2 , and the 2/6 drive gear D 2 / 6 , and the third preliminarily shifted torque is input to the first rotation shaft TM 1 of the third shifting member T 3 .

In addition, the torque of the engine ENG is input to the second rotation shaft TM 2 of the third shifting member T 3 through the first input shaft IS 1 .

As shown in FIG. 3 , since the third preliminarily shifted torque is input to the first rotation shaft TM 1 and the torque of the engine ENG is input to the second rotation shaft TM 2 , the first and second planetary gear sets PG 1 and PG 2 integrally or monolitcally rotate and a sixth shift line SP 6 is formed in the third shifting member T 3 . Therefore, a gear ratio of D 6 is output through the third rotation shaft TM 3 that is the output member.

[Seventh Forward Speed Stage]

As shown in FIG. 2 , the 1/7 driven gear P 1 / 7 is operably connected to the intermediate shaft CS through the sleeve SLE 1 of the first synchronizer SL 1 , and the second clutch CL 2 and the third clutch CL 3 are operated at the seventh forward speed stage D 7 .

Therefore, the torque of the engine ENG is shifted into the first preliminarily shifted torque through the second clutch CL 2 , the third input shaft IS 3 , the 1/7 drive gear D 1 / 7 , the 1/7 driven gear P 1 / 7 , the intermediate shaft CS, the transfer gear TFG, and the 2/6 drive gear D 2 / 6 , and the first preliminarily shifted torque is input to the first rotation shaft TM 1 of the third shifting member T 3 .

In addition, the torque of the engine ENG is input to the second rotation shaft TM 2 of the third shifting member T 3 through the first input shaft IS 1 .

As shown in FIG. 3 , since the first preliminarily shifted torque is input to the first rotation shaft TM 1 and the torque of the engine ENG is input to the second rotation shaft TM 2 , a seventh shift line SP 7 is formed in the third shifting member T 3 . Therefore, a gear ratio of D 7 is output through the third rotation shaft TM 3 that is the output member.

[Eight Forward Speed Stages]

As shown in FIG. 2 , the 8/R drive gear D 8 /R is operably connected to the second input shaft IS 2 through the sleeve SLE 2 of the second synchronizer SL 2 , and the first clutch CL 1 and the third clutch CL 3 are operated at the eight forward speed stages D 8 .

Therefore, the torque of the engine ENG is shifted into the fourth preliminarily shifted torque through the first clutch CL 1 , the second input shaft IS 2 , the 8/R drive gear D 8 /R, the idle gear IDG, the 8/R driven gear P 8 /R, the intermediate shaft CS, the transfer gear TFG, and the 2/6 drive gear D 2 / 6 , and the fourth preliminarily shifted torque is input to the first rotation shaft TM 1 of the third shifting member T 3 as the inverse rotation speed.

In addition, the torque of the engine ENG is input to the second rotation shaft TM 2 of the third shifting member T 3 through the first input shaft IS 1 .

As shown in FIG. 3 , since the fourth preliminarily shifted torque is input to the first rotation shaft TM 1 and the torque of the engine ENG is input to the second rotation shaft TM 2 , an eighth shift line SP 8 is formed in the third shifting member T 3 . Therefore, a gear ratio of D 8 is output through the third rotation shaft TM 3 that is the output member.

The power transmission apparatus for a vehicle according to the first exemplary embodiment of the present invention may achieve the reverse speed stage and eight forward speed stages by adding two planetary gear sets to a DCT provided with two synchronizers. Therefore, multiple speed stages may be achieved and fuel economy may be improved.

In addition, an interior layout may be simplified, length and weight of the DCT may be minimized by reducing the number of components.

In addition, since even-numbered speed stages and odd-numbered speed stages are achieved by turns by alternately operating two clutches, smooth shift may be achieved.

FIG. 4 is a schematic diagram of a power transmission apparatus for a vehicle according to a second exemplary embodiment of the present invention.

Referring to FIG. 4 , the first synchronizer SL 1 included in the first shifting member T 1 is disposed on the intermediate shaft CS in the power transmission apparatus for a vehicle according to the first exemplary embodiment of the present invention, the first synchronizer SL 1 is disposed on the third input shaft IS 3 according to the second exemplary embodiment.

Therefore, the 1/7 drive gear D 1 / 7 and the 3/5 drive gear D 3 / 5 are rotatably disposed on the third input shaft IS 3 , and the first synchronizer SL 1 operably connects the 1/7 drive gear D 1 / 7 or the 3/5 drive gear D 3 / 5 to the third input shaft IS 3 selectively. In addition, the 1/7 driven gear P 1 / 7 engaged to the 1/7 drive gear D 1 / 7 , and the 3/5 driven gear P 3 / 5 engaged to the 3/5 drive gear D 3 / 5 are fixedly disposed on the intermediate shaft CS.

The constituent elements and shifting processes according to the second exemplary embodiment of the present invention are the same as those according to the first exemplary embodiment except arrangements of the first synchronizer SL 1 and the drive gears and the driven gears related thereto. Therefore, detailed description thereof will be omitted.

FIG. 5 is a schematic diagram of a third shifting member of a power transmission apparatus for a vehicle according to a third exemplary embodiment of the present invention.

Referring to FIG. 5 , the first sun gear S 1 is directly connected to the second sun gear S 2 and the first planet carrier PC 1 is selectively connectable to the second ring gear R 2 such that the first and second planetary gear sets PG 1 and PG 2 being single pinion planetary gear sets include four rotation shafts TM 1 to TM 4 in the third shifting member T 3 according to the first exemplary embodiment of the present invention, but the first sun gear S 1 is directly connected to the second sun gear S 2 and the first planet carrier PC 1 is directly connected to the second ring gear R 2 such that the first and second planetary gear sets PG 1 and PG 2 being the single pinion planetary gear sets include four rotation shafts TM 1 to TM 4 in the third exemplary embodiment.

The four rotation shafts TM 1 to TM 4 of the third shifting member T 3 according to the third exemplary embodiment of the present invention will be described in detail.

The first rotation shaft TM 1 directly connects the first sun gear S 1 to the second sun gear S 2 and is directly connected to the 2/6 drive gear D 2 / 6 .

The second rotation shaft TM 2 is directly connected to the second planet carrier PC 2 and is selectively connectable to the first input shaft IS 1 so as to be operated as a selective input element.

The third rotation shaft TM 3 directly connects the first planet carrier PC 1 to the second ring gear R 2 and is directly connected to the output shaft OS so as to be operated as the output element.

The fourth rotation shaft TM 4 is directly connected to the first ring gear R 1 and is selectively connectable to the transmission housing H so as to be operated as a selective fixed element.

In addition, the third clutch CL 3 is disposed between the first input shaft IS 1 and the second planet carrier PC 2 directly connected to the second rotation shaft TM 2 , and the brake BK is disposed between the first ring gear R 1 directly connected to the fourth rotation shaft TM 4 and the transmission housing H.

The constituent elements of the third shifting member T 3 and shifting processes according to the third exemplary embodiment are the same as those according to the first exemplary embodiment or the second exemplary embodiment except the rotation shafts and the rotation elements connected to the frictional elements. Therefore, detailed description thereof will be omitted.

FIG. 6 is a schematic diagram of a third shifting member of a power transmission apparatus for a vehicle according to a fourth exemplary embodiment of the present invention.

Referring to FIG. 6 , the first sun gear S 1 is directly connected to the second sun gear S 2 and the first planet carrier PC 1 is selectively connectable to the second ring gear R 2 such that the first and second planetary gear sets PG 1 and PG 2 being single pinion planetary gear sets include four rotation shafts TM 1 to TM 4 in the third shifting member T 3 according to the first exemplary embodiment of the present invention, but the first planet carrier PC 1 is directly connected to the second ring gear R 2 and the first sun gear S 1 is selectively connectable to the second sun gear S 1 such that the first and second planetary gear sets PG 1 and PG 2 being the single pinion planetary gear sets include four rotation shafts TM 1 to TM 4 in the fourth exemplary embodiment.

The four rotation shafts TM 1 to TM 4 of the third shifting member T 3 according to the fourth exemplary embodiment of the present invention will be described in detail.

The first rotation shaft TM 1 is directly connected to the first sun gear S 1 , is directly connected to the 2/6 drive gear D 2 / 6 , and is selectively connectable to the second sun gear S 2 .

The second rotation shaft TM 2 is directly connected to the second planet carrier PC 2 and is directly connected to the first input shaft IS 1 .

The third rotation shaft TM 3 directly connects the first planet carrier PC 1 to the second ring gear R 2 and is directly connected to the output shaft OS so as to be operated as the output element.

The fourth rotation shaft TM 4 is directly connected to the first ring gear R 1 and is selectively connectable to the transmission housing H so as to be operated as the selective fixed element.

In addition, the third clutch CL 3 is disposed between the first sun gear S 1 and the second sun gear S 2 , and the brake BK is disposed between the first ring gear R 1 and the transmission housing H.

The constituent elements of the third shifting member T 3 and shifting processes according to the fourth exemplary embodiment are the same as those according to the first exemplary embodiment or the second exemplary embodiment except the rotation shafts and the rotation elements connected to the frictional elements. Therefore, detailed description thereof will be omitted.

FIG. 7 is a schematic diagram of a third shifting member of a power transmission apparatus for a vehicle according to a fifth exemplary embodiment of the present invention.

Referring to FIG. 7 , the first sun gear S 1 is directly connected to the second sun gear S 2 and the first planet carrier PC 1 is selectively connectable to the second ring gear R 2 such that the first and second planetary gear sets PG 1 and PG 2 being single pinion planetary gear sets include four rotation shafts TM 1 to TM 4 in the third shifting member T 3 according to the first exemplary embodiment of the present invention, but the first planet carrier PC 1 is directly connected to the second ring gear R 2 and the first ring gear R 1 is directly connected to the second planet carrier PC 2 such that the first and second planetary gear sets PG 1 and PG 2 being the single pinion planetary gear sets include four rotation shafts TM 1 to TM 4 in the fifth exemplary embodiment.

The four rotation shafts TM 1 to TM 4 of the third shifting member T 3 according to the fifth exemplary embodiment of the present invention will be described in detail.

The first rotation shaft TM 1 is directly connected to the first sun gear S 1 and is directly connected to the 2/6 drive gear D 2 / 6 .

The second rotation shaft TM 2 directly connects the first planet carrier PC 1 to the second ring gear R 2 and is selectively connectable to the first input shaft IS 1 .

The third rotation shaft TM 3 directly connects the first ring gear R 1 to the second planet carrier PC 2 and is directly connected to the output shaft OS so as to be operated as the output element.

The fourth rotation shaft TM 4 is directly connected to the second sun gear S 2 and is selectively connectable to the transmission housing H so as to be operated as the selective fixed element.

In addition, the third clutch CL 3 is disposed between the first input shaft IS 1 and the second rotation shaft TM 2 , and the brake BK is disposed between the fourth rotation shaft TM 4 and the transmission housing H.

The constituent elements of the third shifting member T 3 and shifting processes according to the fifth exemplary embodiment are the same as those according to the first exemplary embodiment or the second exemplary embodiment except the rotation shafts and the rotation elements connected to the frictional elements. Therefore, detailed description thereof will be omitted.

FIG. 8 is a schematic diagram of a third shifting member of a power transmission apparatus for a vehicle according to a sixth exemplary embodiment of the present invention.

Referring to FIG. 8 , the first sun gear S 1 is directly connected to the second sun gear S 2 and the first planet carrier PC 1 is selectively connectable to the second ring gear R 2 such that the first and second planetary gear sets PG 1 and PG 2 being single pinion planetary gear sets include four rotation shafts TM 1 to TM 4 in the third shifting member T 3 according to the first exemplary embodiment of the present invention, but a compound planetary gear set of Ravingneaux type in which a double pinion planetary gear set and a single pinion planetary gear set are combined with each other and a planet carrier and a ring gear are used in common is used to include four rotation shafts TM 1 to TM 4 in the sixth exemplary embodiment.

The four rotation shafts TM 1 to TM 4 of the third shifting member T 3 according to the sixth exemplary embodiment of the present invention will be described in detail.

The first rotation shaft TM 1 is directly connected to the second sun gear S 2 and is directly connected to the 2/6 drive gear D 2 / 6 .

The second rotation shaft TM 2 is directly connected to a common planet carrier PC 12 and is selectively connectable to the first input shaft IS 1 .

The third rotation shaft TM 3 is directly connected to a common ring gear R 12 and is directly connected to the output shaft OS so as to be operated as the output element.

The fourth rotation shaft TM 4 is directly connected to the first sun gear S 1 and is selectively connectable to the transmission housing H so as to be operated as the selective fixed element.

In addition, the third clutch CL 3 is disposed between the first input shaft IS 1 and the second rotation shaft TM 2 , and the brake BK is disposed between the fourth rotation shaft TM 4 and the transmission housing H.

The constituent elements of the third shifting member T 3 and shifting processes according to the sixth exemplary embodiment are the same as those according to the first exemplary embodiment or the second exemplary embodiment except the rotation shafts and the rotation elements connected to the frictional elements. Therefore, detailed description thereof will be omitted.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.